Device to accelerate the boiling of a liquefied gas



G. DALLE Aug. 12, 1969 DEVICE T0 ACCELERATE THE BOILING OF ALIQUEFIED GAS 5 Sheets-Sheet 1 Filed Jan. 5, 1968 INVENTOR GERARD DALLE BY v ,9

J? 12,62 V i/M ATTORNEYS Aug. 12, 1969- DALLE 3,460,351

DEVICE TO ACCELERATE THE BOILING OF A LIQUEFIED GAS Filed Jan. 5. 1968 5 Sheets-Sheet z GERARD DALLE ATTORNEYS DEVICE TO ACCELERATE THE BOILING OF A LIQUEFIED GAS 5H) BHOSSBBd GERARD DALLE ATTORNEYS 3,460,351 DEVICE T ACCELERATE THE BQILWG OF A LIQUEFIED GAS Gerard Dalle, Poitiers, France, assignor to Geigy Chemical Corporation, Ardsley, N.Y. Filed Jan. 5, 1968, Ser. No. 696,063 Claims priority, application France, Jan. 5, 1967,

90,02 Int. Cl. F17c 7/02; B67b 7/24 US. CI. 62-50 15 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a device designed to accelerate the boiling of a liquefied gas under pressure when the liquefied gas is subjected to a pressure reduction of a nature to cause its boiling.

This invention is more specifically applicable to the field of aerosol dispensers, in which the device in question constitutes a new means of accelerating the boiling of a propellant composed of the liquefied gas under pressure. Aerosol dispensers equipped with the device of the present invention can accordingly make use of a propellant selected from among gases whose physical properties would otherwise not be very suitable for such a purpose.

There will be described more specifically hereunder the preferred area of application of the present invention, namely, the area of aerosol dispensers of the type comprising:

A propellant cartridge having a push-button valve thereon and containing a liquefied gas serving as propellant;

A nozzle assembly having a venturi nozzle therein and producing by the flow of the gas therethrough the suction, ejection and spraying of a product to be dispensed in the liquid phase and containing at least one active agent; and

A product container containing the liquid phase product, which container can be coaxial with and surround the propellant cartridge and contain it, or can be placed alongside the propellant cartridge.

Such dispensers are intended to be used while they are held in a vertical position, and must be able to discharge the propellant gas under a relatively constant driving pressure over an extended period of time and without it being necessary to shake them, even when they are used at a relatively low ambient temperature.

The minimum value of the driving pressure which must be produced depends on many factors, among which are:

The quality of the spray desired (air dispersed aerosol or surface covering spray);

The nature of the more or less volatile vehicle in which the active agent is carried; and

The relative quantities of the available gases and liquids, which are governed by the capacities of the apparatus.

As a rule, the minimum value of the driving pressure is approximately 1 kg./cm. for air dispersed aerosols. The gases available from a practical and economic standpoint to produce such a pressure are few in number. They are, essentially:

(a) Fluorochlorinated hydrocarbons, among others chlorodifiuoromethane (F22) (boiling point -E=40.8 C.)

3,460,351 Patented Aug. 12, 1969 and dichlorodiflu-oromethane (F12) (E=27.8 C.):

(b) Propane (E=42.2 C.);

(c) Isobutane (E=l1.7 C.);

(d) Butane (E=0.5 C.);

(f) Vinyl chloride (E=14 0).

However, all these compounds have drawbacks. The fluorochlorinated derivatives are heavy gases by means of which air dispersed sprays can be obtained only at the cost of a considerable consumption of gas;

Propane has a vapor tension ranging to about 20 bars at 50 C. and causes serious problems in connection with the resistance and tightness of the propellant cartridge;

The other gases mentioned have boiling points which approach the ambient temperature too closely to permit maintaining a suflicient pressure, notably in cases of severe use conditions, e.g. low ambient temperatures.

The prior art has therefore sought to accelerate and regulate the boiling of these other gases to permit their being used as propellants. In particular, the following means have been suggested and have been used in the prior art aerosol dispensers and the packing of gases under pressure.

In one arrangement, a heating element is introduced into the cartridge of the liquid propellant. Such an arrangement is costly and unacceptable for an aerosol dispenser, which generally has a small volume, and the various components of which cannot be disassembled due to the fact that, once empty, such a dispenser is as a rule not used again.

According to another known arrangement, the valve is fed not with the gaseous phase, but with the liquid phase. By this means, the flow of the propellant gas is uniform whatever may be the position of the reservoir and the manipulations to which it may be subjected. This system is completely unworkable for aerosol dispensers, because the ejector nozzle must be traversed by a stream of gas.

Finally, it has been suggested to combine with the liquefied gas a material that is a gas even at very low temperatures and which would be dissolved in the liquefied gas, or to add materials which would create a gas in situ, for example by the effect of hydrogen peroxide on fibrin. The practical application of such a process is very difficult.

The device according to the invention accelerates and regulates the boiling of a liquefied propellant, and is first of all designed to cope with the drawbacks of the previous devices referred to above.

The invention is intended in particular, on account of its exceeding low cost, for use in aerosol containers sold at relatively low prices, and in which the propellants can be the gases mentioned above but considered unemployable for such purpose.

According to the invention, the device for accelerating the boiling of a liquefied gas or a mixture of liquefield gases under pressure contained in an enclosure in which a state of liquid-vapor equilibrium has been established, is characterized by the fact that it is made up of a body which is insoluble in the liquefied gas or mixture of gases and is at least partially immersed in the liquefied gas or gases, the body containing at least one cavity in communication with the liquefied gas through an opening in the body and the inner end of which cavity is located at a level higher than that of the opening, the cavity being at least partially filled with the vapor phase of the gas or gases in question.

It has, in fact, been established that with this device in the enclosure containing the liquefied gas, there is produced the astonishing result of acceleration and regulation of the boiling of the liquefied gas when the pressure in the enclosure is changed, notably when the enclosure is opened to the air.

More specifically, at the time when the pressure of the vapor phase is reduced, for example by using it to dispense a product, there is produced at the level of the opening of said cavity a boiling surface, generating gas and accelerating boiling at the same time, which effect insures, simultaneously with the boiling produced at the open surface of the liquid, a compensation for the drop of pressure in the enclosure.

A posteriori, the following explanation can be given for this phenomenon. In an enclosure which does not contain the device according to the invention, in the absence of any shaking, the heat required for the boiling of the liquid is supplied by a zone close to the open surface of this liquid; the aggregate of the liquid mass does not cool appreciably and the gas flow slows down as the boiling continues, in relation to the cooling of the abovementioned open surface.

By the addition of the device according to the invention, there is created a new boiling surface which is added to that of the open surface and, moreover, brings about the acceleration of the boiling at the open surface through the supply of heat insured by the rising bubbles which stir the liquid mass.

The device according to the invention is moreover es pecially advantageous when it is advisable to avoid the lowering of the pressure in the enclosure.

According to a preferred field of application of the invention, the enclosure consists of an aerosol dispenser container, the liquefied gas serving as propellant for the spraying of an active agent. In this case, the invention makes possible aerosol dispensers equipped with a device pursuant to the invention and in which the propellant is a gas of the type referred to above and not used at present in a similar field.

In one preferred form of the invention, a cavity is the space within a hollow tube which is open at one end and closed at the other end and partially immersed in the liquid, the opening being disposed at the lower portion or lower end. Such a tube will hereinafter be referred to as a bubble tube.

In a second preferred form of the invention, the cavity is the space within a bent back hollow tube, the two ends of which are located at the bottom of the enclosure.

In a third form of the invention, there are a plurality of cavities distributed at least on the surface of a spongy or porous body, the body being immersed in the liquefied gas in the enclosure.

Other features of the invention will be clear from the following description, taken with the accompanying drawings, in which:

FIG. 1 is a vertical cross section of an aerosol dispenser with a double reservoir, the propellant cartridge having a bubble tube therein;

FIGS. 2A2E are diagrams of comparative tests of the discharge characteristic of several propellant cartridges, one of which contains a bubble tube;

FIG. 3 is a vertical cross section of a propellant cartridge containing a bent-back bubble tube; and

FIG. 4 is a vertical cross section of a propellant cartridge containing a porous body.

The specific examples of the present invention which will be described hereinafter, are particularly useful in the area of aerosol type push-button dispensers.

As shown in FIG. 1 of the attached drawings, a product container 1 of an aerosol dispenser contains a liquid active agent 2 to be dispensed.

Container 1 is closed by a cover 4 having a depending portion on which is mounted a propellant cartridge 5 containing the propellant 6, such as a liquefied gas, the kinetic energy of which supplies the energy for spraying of liquid 2. Cover 4 also carries valve means comprising an obturator or obturators required for controlling fluid flow and has an ejector with a push-button 9 thereon having a spray nozzle therein, the outlet aperture of which is seen at 10.

Active agent 2 is conducted to the ejector by a dip tube 3. The open surface AA of the liquefied gas 6 defines in the cartridge 5 the boundary between the volumes occupied respectively by the liquid phase 6 and vapor phase '7.

Pursuant to this invention, a bubble tube 8 is freely disposed inside the cartridge 5. The hollow interior of the bubble tube constitutes a cavity and has the upper end 11 thereof closed, but the lower end 1011 is open.

When the dispenser is at rest, bubble tube 8 is partially filled With liquid, and the remainder of the interior is filled with gas. Excluding capillary phenomena and any effect due to the presence of initially imprisoned air, the level a of the liquid in bubble tube 8 is at the plane of the open surface AA of the liquefied gas. The gas occupies the remaining volume of bubble tube 8 between this level a and upper end 11.

, Preferably, bubble tube 8 is of polyethylene or aluminum. However, it may be made of any other substance sufiiciently strong so that it will not break under the eifect of the normal shocks to which the dispenser may be subjected, and which will cause no corrosion to occur in cartridge 5 nor in the components of the obturator, and which is insoluble in the liquefied gas and devoid of chemical afiinity with respect to it. Limited interactions can nevertheless be permitted, as for example a slight swelling of bubble tube 8.

The inside diameter of bubble tube 8 can be less than 1 mm, but from a practical standpoint the inside diameter of the tube 8 ranges from 1 to 3.5 mm. and, preferably, from 2 to 3 mm. More specifically, the inside diameter of bubble tube 8 must "be such so that the liquid contained therein can be expelled without delay when lowering of the pressure of the vapor phase 7 occurs; its specific determination would require knowledge of the size of the propellant cartridge, volume of the vapor phase 7, the volume of the gas isolated in tube 8 and the height of liquid 6 in reservoir 5. In practice, the inside diameter of bubble tube 8 does not, as a rule, exceed 4 mm. for cartridges 5 having a volume of 50 ml. and 5 mm. for cartridges 5 having a volume of ml.

The thickness of the bubble tube 8 is not an important factor; it need only be such as to insure suitable rigidity, taking into account the above-mentioned swelling which may occur.

The length of bubble tube 8 is less than or equal to the length of the longest tube 13 that can be introduced into cartridge 5 and greater than the greatest depth of liquid that can be contained in said cartridge 5. This depth does not as a rule exceed 3 5 of the distance H which separates the bottom of cartridge 5 from the propellant gas discharge aperture 12. This preferred size forces tube 8 to remain partially immersed without being able to sink completely to the bottom of cartridge 5 nor float on the open surface of liquid 6. On the other hand, bubble tube 8 has its lower end 10a close to the bottom of cartridge 5, which enables it to properly fulfill its function.

Bubble tube 8 can be straight or slightly curved, no special importance being attached to these variations in shape.

When push-button 9 of the dispenser is depressed, the propellant gas stored in the space occupied by vapor phase 7 in cartridge 5 is released and causes the spraying of active agent 2. As a result of this, the pressure of the vapor phase 7 drops, which causes the boiling of liquid 6 at the level of open surface AA. The pressure drop is instantaneously transmitted through the liquid to the gas isolated in the upper section of bubble tube 8.

The gas isolated between level a and upper end 11 of bubble tube 8 expands and propels the liquid in the tube toward the lower end 10a of bubble tube 8.

When tube 8 is completely filled with the gas, there is formed a liquid-gas contact surface within liquid 6 and at end a of the tube 8 which becomes a generator of gas bubbles. As a matter of fact, this small surface provides, through the boiling which prevails there, an additional supply of gas which adds itself to that produced on the open surface AA of liquid 6.

The efficiency of this first embodiment of the device according to the invention has been verified in the course of experiments, the results of which are shown in the diagrams of FIGS. 2A-2E, in which the pressures P in kg./ cm. are plotted on the Y-axis and the times t in seconds are plotted on the X-axis.

Measurements were taken, at ambient temperature around 18 C., of the pressures above a nozzle having a collar diameter of 0.5 mm., fed by four glass flasks of 150 ml. each, filled with isobutane, in the course of 5 successive sprayings of 10 seconds, spaced 2 minutes apart. The pressures in each flask for each spraying are shown in the respective FIGURES 2A-2E.

Flask I was shaken during the tests.

Metal chips were introduced into flask II.

Flask III has therein a bubble tube 8 according to the present invention.

Flask IV was used without shaking.

The pressure curves obtained with flask I show a proper behavior of the dispenser, which was able to function during all of the sprayings at a pressure in excess of 1 kg./ cm. The gas flow was controlled by the regular shaking of flask I, which thus caused a continuous and sufiicient supply of the internal heat of the liquid to its open surface where the boiling was taking place.

Conversely, the pressure curves obtained with flask IV, which was held vertically without shaking, show that the pressure drops rapidly at 300 g./cm. and then varies irregularly with the sudden and random appearance of vapor bubbles in the liquid.

Flask III equipped with bubble tube 8 shows a relatively orderly pressure curve, the values of which range above 1 kg./cm. as in the case of flask I. Bubble tube 8, simply an inverted tube, acts here as a permanent and regular generator of bubbles and produces almost the same effect as the method of shaking.

Finally, the behavior of flask II is very irregular. The pressure curve drops very rapidly to about 300 g./cm. and even lower, and rises only in the course of the first and third sprayings.

These tests show that the presence of a bubble tube permits using, without constant shaking, which is very important as far as portable sprayers are concerned, propellant gases with a lower vapor pressure than that of propane, such as isobutane, vinyl chloride, isobutylene and butane. It follows from this that cartridge 5 can be filled with a propellant less costly than propane.

According to a second embodiment shown in FIG. 3, the bubble tube is bent double.

This bent bubble tube consists of a flexible tube 14of polyethylene, for examplecut to a length twice that required for a single tube, and bent at its middle until its ends 15 touch, and placed in reservoir 5 with the open ends 15 resting on the bottom of the latter.

In this way, there is provided a very eflicient bubble tube, the inside diameter of which can be from 1 to 3.5

The functioning of bent tube 14 is identical to that of bubble tube 8 which has been previously described.

The third embodiment shown in FIG. 4 comprises a porous body 16 placed on the bottom of reservoir 5. Porous body 16 has on its outer surface a large number of cavities 17, which are closed on the inner end and which can retain fractions of gas by adsorption.

Preferably, porous body 16 is vermiculite, pumice stone, wood charcoal or a scrap of rough bone.

All these bodies have an outer surface, the corrugations of which are visible to the eye; they have a cellular structure and cavities opening outwardly and closed on the inner end; they are chemically inert with respect to the components of the dispensing apparatus and to the liquefied gas; their mechanical resistance is sufiicient to withstand normal shocks; and their density is such that they remain at the bottom of cartridge 5.

The preferred porous bodies have the advantage of inducing boiling for more than one month after their introduction into a cartridge 5, without preliminary shak- This feature differentiates them from other porous bodies such as soft wood, agglomerated wood, resinous wood, frit, cement, plaster, slate, crystallized sulphur and earthware, for which it is necessary, in the event that the dispenser is not used for an extended period of time (15 days, for example), to shake the dispenser for the purpose of restoring physical contact between the porous body and the vapor phase.

This difference of behavior between the two categories of bodies probably stems from the fact that the preferred porous bodies are not wet by the liquefied gas and consequently the gases adsorbed by them are not dissolved in the liquid.

The dimensions of the fragments of porous bodies are such that there is no need, for practical reasons, to go below a volume equivalent to that of a grain of Wheat. Preferably, for 50 to ml. reservoirs, the fragment has approximately the volume of a sphere 5 mm. in diameter, and its shape can be any shape whatever and range from a spheroid, which is completely immersed, to a very elongated rod, which may be only partially immersed. It is obvious that the fragments can be of greater size and that several fragments can be used simultaneously. It is advisable, however, that these fragments not be able to penetrate into the dispenser valve nor take too much space in cartridge 5 because they will reduce the amount of propellant 6 which can be stored.

At the time of their preparation, efforts must be made to cut the porous bodies in a way such that they present in all positions a cellular surface capable of generating gas bubbles when this surface is turned toward the bottom. In particular, in cases where the cavities develop in a preferential direction, or rest against a compact inner core, the substance must be cut in a way such that the body will present, in all the positions that it may assume, a cellular surface turned toward the bottom of the reservoir.

The porous bodies according to the invention function in the same manner as the tubes. When the dispenser valve is set in motion, the pressure of the gas below the open surface of cartridge 5 diminishes. This pressure drop is transmitted through the liquid to the small gas bubbles retained in the cavities of the lower section of porous body 16, which expand until they spill out of their cavities 17. The liquid-gas contact surfaces bordering on these cavities 17 become boiling surfaces where gas bubbles are produced which rise toward the open surface, bringing along with them a certain quantity of heat which accelerates the boiling produced on the open surface.

It is obvious that these porous bodies can fulfill their function only to the extent that gas particles have previously been adsorbed by them. The triggering occurs in a very natural way by reason of the very adsorbent power of the porous body in contact with the liquid. If, for any reason whatsoever, such as a protracted storage, triggering does not occur, a mere shaking, bringing the porous body in contact with the gas phase, is sufficient to bring about the boiling as soon as the obturator is opened.

The efficiency of this third embodiment to accelerate boiling is comparable to that of the bubble tube.

It is quite obvious that the device according to the invention to accelerate the boiling of a liquefied gas can be the subject of many other applications which do not depart from the scope of the invention.

What is claimed is:

1. A device for accelerating the boiling of a liquefied gas, comprising an enclosure adapted to contain liquefied gas under pressure in which a state of liquid-vapor equilibrium has been established, and a body which is insoluble in the liquefied gas positioned in said enclosure, said body having therein at least one cavity having the inner end thereof closed and having an opening opening out of the body below the level of the closed inner end of the cavity, said opening being positioned in the enclosure at a level below the level at which the liquefied gas will normally occupy in the enclosure.

2. A device as claimed in claim 1 in which said enclosure is an aerosol dispenser container adapted to utilize liquefied gas as a propellant.

3. A device as claimed in claim 1 in which said body is a hollow tube closed at one end and positioned in said enclosure with the closed end uppermost, said cavity being the hollow interior of the tube and said opening being the open lower end of the tube.

4. A device as claimed in claim 3 in which said tube is polyethylene.

5. A device as claimed in claim 3 in which said tube is aluminum.

6. A device as claimed in claim 3 in which the inner diameter of said tube is from 1-5 mm. and said enclosure has a volume of 50-150 ml.

7. A device as claimed in claim 3 in which the length of said tube is less than the greatest inside dimension of said enclosure and greater than /5 the inside height of the enclosure.

8. A device as claimed in claim 1 in which said body is a hollow tube open at both ends and bent double and positioned in said enclosure with the open ends down, the cavity being the hollow interior of the tube and said opening being the open ends of said tube.

9. A device as claimed in claim 8 in which said tube is polyethylene.

10. A device as claimed in claim 8 in which said tube is aluminum.

11. A device as claimed in claim 8 in which the inner diameter of said tube is from l-5 mm. and said enclosure has a volume of 50-150 ml.

12. A device as claimed in claim 1 in which said body is a porous body containing a plurality of cavities, said body resting on the bottom of the enclosure with at least some of said cavities opening out of the lower surface of said body.

13. A device as claimed in claim 12 in which said porous body is of a material taken from the group consisting of vermiculite, pumice stone, wood charcoal and scraps of rough bone.

14. A device as claimed in claim 12 in which said enclosure has a volume of from 50-150 ml., and said porous body has a volume equivalent to that of a sphere approximately 5 mm. in diameter.

15. A device as claimed in claim 12 in which said body has cavities opening out of all of the surfaces thereof.

References Cited UNITED STATES PATENTS 2,084,297 6/1937 Martin 62-50 2,729,068 1/1956 Mitchell 62-50 2,805,554 9/1957 Schachtsick 6-250 2,892,317 6/1959 Holmes 62--50 2,954,678 10/ 1960 Mahon et al. 62-50 LLOYD L. KING, Primary Examiner U.S. Cl. X.R. 62294; 2223 

